A problem that has been perplexing and long standing is the cracking of the material in close proximity to the boroscope access hole. Heretofore, the access hole was plugged by seating the plug on a boss formed at the access hole on the exterior of the engine.
I have found that I can obviate or at least minimize this problem by the free float mounting of the plug together with the judicious seating arrangement, which lessens the likelihood of fluid in the respective casings to migrate to the other casings. This invention contemplates spring loading the plug which compensates for dimensional tolerance in the axial stack-up as well as providing support for the plug which allows relative motion between the inner most casing and the outer casing.